1. Field of the Invention
The present invention relates to a method of working a structure for working a workpiece into a structure having a cavity of a desired shape, and more particularly, it relates to a method of working an optical component mold (structure) for forming an optical component such as a Fresnel lens or an LED component by molding an optical element (electronic component) such as a light-emitting diode (LED) chip with a resin material such as silicone resin, for example.
2. Description of the Background Art
Working of a mold material with a conventional four-spindle lathe-type cutting/working apparatus is now described with reference to FIGS. 13A and 13B. In general, a lathe-type cutting/working apparatus 101 (four-spindle lathe-type cutting/working apparatus driven at least in four directions along the X-, Y-, Z-and C-axes, for example) is employed for working a mold material (workpiece) 102 with a cutting tool (turning tool) 103 such as a single-crystalline diamond tool thereby working an optical component mold (structure) for molding an optical component such as a Fresnel lens. This method is carried out in the following manner, for example:
First, mold material 102 is mounted on a mold material mount portion 104 of lathe-type cutting/working apparatus 101, and rotated about the C-axis (rotation center 105) of cutting/working apparatus 101 in a rotational direction (clockwise direction 109 in FIG. 13A). Then, mold material 102 is cut along center 105 forming the axis of rotation of rotated mold material 102 with cutting tool 103, thereby forming a Fresnel lens (optical component) molding cavity 106 having a circular opening and a working surface corresponding to the shape of the Fresnel lens on a work surface 107 of mold material 102.
At this time, a desired number of peripheral grooves each having a desired shape are formed on the working surface of cut cavity 106 concentrically with center 105 of the axis of rotation (C-axis), for forming mold material 102 (cavity part 108) having one cavity 106.
Therefore, a cavity block (split mold) having a desired number of cavities 106 is formed by aligning and combining the desired number of cavity parts 108 each having one cavity 106 with each other.
According to another working method employing cutting/working apparatus 101, mold material 102 is mounted on mold material mount portion 104 of cutting/working apparatus 101 and rotated about the C-axis of apparatus 101 as described above. Then, the steps of cutting one cavity 106 about rotation center 105 of mold material 101 with cutting tool 103 and thereafter moving (shifting) the worked position of worked mold material 102 are so repeated as to form a cavity block (split mold) having a desired number of cavities 106 by working the desired number of cavities 106 on mold material 102.
Such working of the mold material with the aforementioned conventional four-spindle lathe-type cutting/working apparatus is disclosed in FIG. 4 of Japanese Patent Laying-Open No. 07-241918 (1995) and description related thereto, for example.
The aforementioned working with lathe-type cutting/working apparatus 101 may be replaced with electron beam lithography. However, the electron beam lithography requires a considerable number of trials and errors in order to obtain optimum exposure distribution, and worked cavities 106 are small. Therefore, a mold formed by this lithography is so inferior in working efficiency that the same is not yet put into practice.
As hereinabove described, an optical component mold (split mold serving as a structure) for molding an optical component such as a Fresnel lens is generally worked with lathe-type cutting/working apparatus 101.
However, setup times are required for working a desired number (a large number) of cavity parts 108 (single cavities 106) respectively as hereinabove described, and a mold (split mold) having a desired number (a plurality) of cavities cannot be efficiently cut for efficiently manufacturing the optical component mold. Therefore, the productivity of the optical component mold (structure) cannot be efficiently improved.
When cavity parts 108 are aligned and combined with each other as described above, a step is easily formed on the combinational reference surface (work surface 107) of the formed cavity block. Therefore, a long time is required for flattening (flushing) this reference surface (107). Consequently, the productivity of the optical component mold (structure) cannot be efficiently improved in the working of (the working method for) the optical component mold.
Further, it is remarkably difficult to precisely arrange cavities 106 formed in mold material (workpiece) 102 at a desired pitch.
In the working of the optical component mold for molding an optical component such as a Fresnel lens, the working surface of the Fresnel lens must be mirror-finished, in order to improve the transparency of the lens or the reflectivity of a reflector.
In the aforementioned working, however, no sufficient desired cutting speed is obtained particularly in a case of cutting a hardly cuttable material such as cemented carbide, and hence working resistance is so increased that the working surface (concave surface, for example) cannot be mirror-finished.
In the case of working the optical component mold, therefore, the working surface formed on the mold cannot be efficiently mirror-finished, and a high-quality working surface cannot be efficiently worked.
In relation to the optical component mold (structure) for molding an optical component such as a Fresnel lens, further, working of an optical component molding cavity having an opening of a desired shape and a nonspherical working surface may be required, in addition to the cutting of cavity 106 having an axisymmetric circular opening and a spherical working surface (concave surface).
However, such a cavity cannot be efficiently worked in the aforementioned working method employing rotation center 105 as the axis of rotation. Thus, an optical component molding cavity having an opening of a desired shape and a nonspherical working surface cannot be efficiently worked in the working (method) of the optical component mold.